See this article in the Hindustan Times. The article has a noticeable pro-India bias, but seems to cover the material factually.
In brief, it seems that this new map is a power-play on the part of Pakistan's Prime Minister, Imran Khan. He is leveraging his close relationship with China, and the current border tensions between China and India, to expand political control into contested territories. Assumedly the hope is that India will back down in the face of a two-front threat; it's one thing to contest the comparatively small border between India and China, but quite another to expand that to the contested territories, much less the entire border of Pakistan. India could 'reasonably' be expected to focus more on the established India-China border than on territories that have historically been disputed, though given the emotional tenor of India-Pakistan relations, I doubt that will be the case.
This also shows intentions to end the Kashmir separatist movement, which would set up the region as an independent state.
Note that Pakistan is taking a page from China's playbook, here. This kind of 'cartography conquest' — taking over an area by implication merely by changing lines on maps — is precisely how China began exerting its territorial rights to the South China Sea. If Pakistan follows that model, we can expect them to begin establishing military bases in strategic regions of Kashmir to defend against Indian incursions on 'Pakistani' territory; efforts at establishing political dominance won't begin until after the area is secured.
The FATA merger was approved by normal political means back in 2018, but that does indicate that Pakistan is moving to absorb administrative territories into its main sovereign body.